Audio policy: Use surround formats from audio config instead of hardcoded

This is a follow-up to ag/3835377, where the intention was to
use SURROND_FORMATS array, which is lately been replaced by
an array from APM's config.

Bug: 67479735
Bug: 117602867
Test: make
Change-Id: I31f63856d8fb06ff9ac0f03b9ec1600f0fcee30b